1. Field of the Invention
This invention relates to methods for the removal of plasma fluid from a patient in need thereof, including those in what may be called a disease state, for example, congestive heart failure or moderate renal insufficiency, both of which are typically characterized by fluid overload. The invention also relates to intravascular devices for effecting the plasma fluid removal.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98.
There are a number of techniques described in the art for removing plasma fluid from a patient. Many patients treated using some of the more conservative of these techniques, such as high dose diuretics or cardiac inotropes fail to adequately respond. In such cases, the use of more invasive, risky, expensive, and/or labor-intensive therapies, such as intermittent hemodialysis or continuous veno-venous hemodialysis or hemofiltration are indicated. While these extracorporeal techniques are traditionally utilized to treat kidney failure, in the presence of fluid overload they can instead result in the removal of bulk fluids by the use of hydraulically, or pump-driven ultrafiltration across a dialyzer (i.e. “an artificial kidney”). It is the extracorporeal processing of blood in these prior art techniques that makes them less than optimal for the desired purposes.
The U.S. patent literature includes a number of prior patents, which, for the sake of easy understanding have been divided into four categories. The first category is one dealing with so-called “probes.” These patents; U.S. Pat. Nos. 5,706,806, 5,607,390, 5,735,832 and 5,106,365, generally disclose devices having sealed ends and which allow fluid to flow to the end of the probe and then back. These devices are made for insertion into body tissues or fluids and are used for diagnostic, not treatment purposes. When using these devices, the analyte of interest diffuses into the probe and then out to an instrument, typically, a measuring instrument. These devices allow monitoring of a patient's pH, oxygen, sodium, potassium, etc. levels in the tissue of interest (blood, muscle, gut, brain, etc).
The second category includes so-called intravascular devices for plasmapheresis. There are a number of these patents by Gorsuch and Co-workers. These patents disclose the diffusion of plasma across semi-rigid membranes in highly complex shapes, but do so in order to remove deleterious plasma proteins. They do not specifically address the removal of fluid/water, even though a “byproduct” of the described techniques is removal of the fluid in which the deleterious proteins reside. In fact, in traditional plasmapheresis, there is no desire or intent to remove fluid per se, so that usually, the water volume is intentionally restored by re-infusing sterile fluids. In addition, some complex devices have been designed to remove targeted proteins from the extracorporeal plasma, and then return the rest of the plasma to the patient (as disclosed in Gorsuch U.S. Pat. No. 4,950,224 and 5,224,926). Additionally, Gorsuch U.S. Pat. No. 5,735,809 states “ . . . the separated plasma may be treated for removing antibodies, antigens, pathogens, toxins and other undesirable materials.” In Gorsuch, there is no teaching of merely removing fluid in the treatment of volume-overload states. Gorsuch, in U.S. Pat. No. 5,980,478, specifically indicates a desire to be able to remove the plasma fluid in its entirety and replace fluids separately as deemed necessary. This is in essence, a “poor man's dialysis,” and much is made of the fact that it would preclude the need for purchasing dialysis equipment. Gorsuch refers to this technique as “PUT,” as in Plasma Ultrafiltration Therapy. This device still removes plasma with all its constituent proteins. (both good and bad), because Gorsuch specifically makes note of a sieving coefficient cutoff of between 2×104 and 4×106 Daltons. The reason for this is that this method utilizes the older Gorsuch plasmapheresis technology. This presents a problem because the method is not safe for patients since the high volumes of ultrafiltrate will contain many important and beneficial proteins, and the patient may be seriously jeopardized if the fluid is continuously discarded.
The third category includes patents directed to intravascular hemodialysis devices, such as U.S. Pat. Nos. 4,235,231; 5,968,004; and 5,980,478. U.S. Pat. No. 5,902,336 is directed not to an intravascular device, but rather to a device surgically connected to a blood vessel and drains directly into the patient's own bladder for fluid removal.
The fourth category includes U.S. Pat. No. 4,563,170; 5,360,397; 6,030,358; 6,238,366; and 6,234,991. The '170 and '397 patents are not relevant since they are extracorporeal in nature and are variations on traditional blood purification devices such as hemodialysis. The '358 patent is not relevant since it discloses a microcatheter to deliver a therapeutic agent into a tissue. The '366 patent is not relevant since it is an extracorporeal fluid management device to help nursing staff keep track of input/output so as to balance fluid administration. Finally, the '991 patent is not relevant because it describes a method of enhancing peritoneal dialysis clearances.